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My Packs: IYNA (Neuroscience) > Lesson 5-6: Vision > Flashcards

Lesson 5-6: Vision Flashcards

1
Q

What is light?

A

A form of electromagnetic radiation visible to the naked eye

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2
Q

What is visible light?

A

The small set of wavelengths of electromagnetic that our eyes can detect

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3
Q

The ability to ______, _______, and _________ the information from visible light helps the organism to ___ the surrounding environment

A

Detect
Process
Interpret
See

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4
Q

Define:

Reflection

A

The change of direction or “bounce back” of a ray after encountering a new medium

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5
Q

Define:

Refraction

A

The bending of light when it is transferred between different mediums

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6
Q

Different _______ in the eye allow for __________ of light

A

Mediums

Refraction

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7
Q

Define:

Cornea

A

Transparent layer that forms the front of the eye and refracts light

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8
Q

Define:

Iris

A

Pigmentation provides colour for the eye

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9
Q

Define:

Lens

A

Bends light rays to form a clear image on the retina

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10
Q

Define:

Sclera

A

Tough wall of the eyeball

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11
Q

Define:

Aqueous Humour

A

Fluid filling the cornea

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12
Q

What is the aqueous humour fluid composed of? (2)

A

Salt

Water

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13
Q

Define:

Vitreous Humour

A

Fluid that provides support for the eye

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14
Q

What is the vitreous humour fluid composed of? (3)

A

Water
Salt
Protein

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15
Q

What is the function of extraocular muscles?

A

Moves the eye to let us shift focus without head rotation

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16
Q

The ______, ____, _______ and ________ _____ focus light onto ______

A 
Cornea
Lens
Aqueous
Vitreous humour
Retina
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17
Q

What do focusing errors cause? (2)

A

Nearsightedness

Farsightedness

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18
Q

Define:

Retina

A

Layer of tissue at the back of the eyeball with cells that respond to light and send signals to the brain

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19
Q

Define:

Optic disk

A

Origin of blood vessels; where optic nerve exits eye

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20
Q

True or False:

The optic disk has photoreceptors

A

False, the optic disk has no photoreceptors

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21
Q

Define:

Macula

A

Region of the retina densely filled with photoreceptors, contributes to central vision

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22
Q

Define:

Fovea

A

Sub region within the macula with very high visual acuity

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23
Q

The retina is a ________ membrane that lines the ____ of the ___

A

Sensory
Back
Eye

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24
Q

From photoreceptors, order the cells of the retina in order (5)

A 
Photoreceptors
Horizontal Cells
Bipolar Cells
Amacrine Cells
Retinal Ganglion Cells
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25
Q

The optic nerve contains only ________ ____ _____. Other cell types ensure that ganglion cells are sending most _________ information to the _____

A

Ganglion cell axons
Important
Brain

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26
Q

Signal travels in an “______-___” manner in the ______, this produces _____ ____ where ganglion cells leave eye

A

Inside-out
Retina
Blind spot

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27
Q

Does the peripheral retina have a high ratio of photoreceptors to ganglion cells?

A

Yes

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28
Q

What is the ratio of photoreceptors to ganglion cells for the central retina?

A

Lower ratio of photoreceptors to ganglion cells

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29
Q

What does the central retina have lower ratio of photoreceptors to ganglion cells?

A

Good for fine detail

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30
Q

When _____ photoreceptors are connected to a _______ cell, finer details can be encoded by the ________ cell

A

Fewer
Ganglion
Ganglion

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31
Q

Describe the function of:

Rods (2)

A

For motion and black-and-white vision

Function well in low light

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32
Q

Describe the function of:

Cones (2)

A

Colour vision and central vision

Function best in medium-high light

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33
Q

Where are cones located?

A

Concentrated in the fovea

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34
Q

List the 4 steps of G-protein signalling

A

Neurotransmitter binds to receptor coupled with a G-protein
Effector enzyme activated
Second messenger molecules(s) activated
Downstream effects result from chemical cascades

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35
Q

List the 3 steps of phototransduction in rods

A

In darkness, sodium channels gated by small molecule cGMP in rods constantly open and neurotransmitters constantly released
Light activates signaling cascade which reduces intracellular cGMP
Without cGMP, sodium channels close, membrane hyperpolarized, and signalling stops

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36
Q

True or False:

G Protein signalling cascade is similar in rods and cones

A

True

37
Q

Unlike rods, _____ express photopigments that show sensitivity towards specific ___________

A

Cones

Wavelengths

38
Q

Overlap in __________ _______ means brain must use information from all _____ to distinguish between ______

A

Absorption spectra
Three
Colours

39
Q

True or False:

Bipolar and horizontal cells integrate signals from many photoreceptors

A

True

40
Q

Define:

Receptive Field

A

Portion of the visual field that elicits activity by a single retinal ganglion cell

41
Q

What is the function of receptive fields?

A

Allows ganglion cells to transmit information about the light being exposed to the photoreceptors

42
Q

What are the components of the receptive field?

A

Center

Surround

43
Q

Describe:

Center (Receptive Field)

A

Photoreceptors here synapse directly onto bipolar cells

44
Q

Describe:

Surround (Receptive Field)

A

Photoreceptors here contribute indirectly by synapsing onto horizontal cells

45
Q

Horizontal cells modulate _______ ________ ____ activity

A

Retinal Ganglion Cell

46
Q

Horizontal cells form __________ synapses to modulate photoreceptor ______

A

Inhibitory

Output

47
Q

True or False:

Horizontal cells are responsible for the difference in on and off bipolar cells

A

False, horizontal cells are NOT responsible for the difference in on and off bipolar cells

48
Q

Where do signals travel from bipolar cells?

A

Retinal ganglion cells

49
Q

How do retinal ganglion cells respond?

A

similarly to bipolar cells (if a bipolar cell is inhibited, the retinal ganglion cell will be less excited)

50
Q

Visual information enters the brain via _____ _____

A

Optic nerve

51
Q

________ cells that make up the optic nerve exit the eye at the _____ _____. Information from each ___ remains separate at first, but must be __________

A

Ganglion
Optic disks
Eye
Integrated

52
Q

What does decussate mean?

A

Cross

53
Q

Axons decussate at the _____ ______ (left visual field to right __________, and vice versa)

A

Optic chiasm

Hemisphere

54
Q

Where do optic tracts project before signals go to primary visual cortex? Why?

A

Thalamic structures

For intermediate processing

55
Q

What is does the optic tracts go after intermediate processing?

A

Primary visual cortex

56
Q

What does LGN stand for?

A

Lateral geniculate nucleus

57
Q

What is the LGN? (2)

A

A portion of thalamus that processes visual information

Receives projections from optic nerve, and projects to visual cortex

58
Q

___s map directly to ___ cells

A

RGC

LGN

59
Q

Define:

RGC

A

Retinal ganglion cells

60
Q

True or False:

The LGN is separated into 4 layers

A

False, the LGN is separated into 6 layers

61
Q

What are the top four layers of the LGN called?

A

Parvocellular layers

62
Q

What does the parvocellular layers do?

A

Receive inputs from small ganglion cells

63
Q

What are the parvocellular layers sensitive to? (3)

A

Color
Fine detail
Slow moving objects

64
Q

What are the bottom two layers of the LGN called?

A

Magnocellular layers

65
Q

What does the magnocellular layers do?

A

Receive inputs from large ganglion cells

66
Q

What are the magnocellular layers sensitive to?

A

Movement of objects

67
Q

State the location of:

Parvocellular layers

A

Top four layers of the LGN

68
Q

State the location of:

Magnocellular layers

A

Bottom two layers of the LGN

69
Q

Starting from the optic tract, where does the visual inputs go?

A

Optic tract, to LGN, to Primary Visual Cortex (V1)

70
Q

Neurons in __ are ___________ selective

A

V1

Orientation

71
Q

__ neurons respond optimally to _________ bar movements

A

V1

Elongated

72
Q

True or False:

The orientation of the bar determines strength of response of the neurons in V1

A

True

73
Q

What is the orientation selective function of V1 for?

A

Motion and object shape detection

74
Q

_________ inputs from ___ are separated in the ______ ______

A

Binocular
LGN
Visual cortex

75
Q

What does the dorsal streams of V1 involve?

A

Involves area MT (medial temporal visual area)

76
Q

What are the details about the neurons and cells in the MT? (2)

A

Neurons here have large receptive fields responsive to movement
Cells here are direction selective

77
Q

What does the ventral streams of V1 involve?

A

Involves area IT and V4

78
Q

What is the details of the cells in the IT/V4?

A

Cells are orientation and color selective

79
Q

What is the role of the ventral stream?

A

For sensing shape and color

80
Q

What contributes to depth perception?

A

Binocular cues

81
Q

Define:

Binocular cues

A

Visual information is taken from both eyes

82
Q

In binocular cues, why is information taken from both eyes?

A

Information can converge to form a more accurate picture

83
Q

In binocular cues, both eyes serve as individual _________ points to judge ________ and respond to ______ ____

A

Reference
Distance
Visual cues

84
Q

To perceive the colour of an object as the same even under varying illumination, what does it require?

A

Requires illumination of varying wavelengths

85
Q

How does do we achieve colour constancy? (3)

A

Cones register overlapping regions of light reflected by objects in scene
Visual systems determines luminescence and discards
Concludes “true” colour

86
Q

Damage to MT or temporary inactivation causes what?

A

Deficits in visual motion perception

87
Q

Optical flow field is computed and represented by _______ in area __

A

Neurons

MT

88
Q

What is special about neurons in area MT?

A

They are selective for motion direction

89
Q

What are neural responses in area MT correlated with?

A

They are correlated with the perception of motion

My Packs: IYNA (Neuroscience) (7 decks)

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